This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 21 |
| 3 | 63 |
| 4 | 270 |
| 5 | 291 |
| 6 | 2991 |
| 7 | 6102 |
| 8 | 46676013 |
| 9 | 69460293 |
| 10 | 2346534651 |
| 11 | 6313047393 |
| 12 | 23400000651 |
| 13 | 80050617822 |
| 14 | 234065340651 |
| 15 | 234659934651 |
| 16 | 2340000000651 |
| 17 | 2530227348360 |
| 18 | 2934000006591 |